Euphydryas chalcedona chalcedona

Variable (or Chalcedon) Checkerspot

A common butterfly in the late spring and early summer, found easily in the San Gabriel and Santa Monica Mountains, where they use such common plants as monkey flower, paintbrush, Keckiella ternata, and K. cordifolia. Larvae form nests in the earliest stages, and they overwinter as half-grown larvae. If conditions allow, there may be a second brood later in the year, and if conditions are exceptionally dry, larvae may hibernate and emerge a year or more later. But usually caterpillars resume feeding in the early spring and begin flying around May and into the summer, sometimes in large numbers.

As hardy and adaptable as they are, I've never seen chalcedona in the mountains around Big Bear Lake, where one instead encounters Euphydryas editha augustina as the dominant checkerspot. I'm not sure why that is.

The type locality (Mt. Tamalpais in Marin County) is discussed in the Systematics book on p.101. A neotype from Mt. Tamalpais was also designated and can be seen on the BoA website. The first photo below is as close as I could find to the neotype. Within the populations of nom. chalcedona I've had experience with in the San Gabriel and Santa Monica Mountains, there is a black ground color; what varies is the size and tone of the cream-to-white colored macules, and the amount of red, which varies from almost none in some individuals to being fairly prominent in others. And that's within the same population. Visual differences among the chalcedona subspecies can be dramatic.